Means for producing fluid pressure



Nov. 15, Y1932.

w. AVERY 1,887,880

MEANS FOR PRODUCING FLUID PRESSURE Filed Jan. 30, 1930 Patented Nov. 15,1932 i UNITED STATES PATENT OFFICE WILLIAM LEICESTER AVERY, OF LONDON,ENGLAND, ASSIGNOR TO THE RUBBER, GUTTA YEBCHA AND TELEGBAPH WORKSCOMPANY LIMITED, OF LONDON, ENGLAND,

'A Bm'rrsi COMPANY MEANS F03 PBODUCING FLUID PRESSURE Application filedJanuary 30, 1930, Serial No. 424,588, and in Great Britain September 21,1929.

The present inventionis for improvements in or relating to apparatus forproducing super-normal or sub-normal pressure in a fluid system foroperating a brake or brakes,

.5 tr example on the landing wheels of an aeroane.

p The type of such apparatus with which the present invention isconcerned is that comprising a chamber to contain the fluid and means(e. g. a piston) for increasing or reducing the effective volume of saidchamber to suck in or expel fluid through an orifice by relativemovement between two members of the apparatus (e.'g. a cylinder and a.piston).

According to the present invention pressure-applying apparatus of thetype specified is characterized by an operating lever pivoted toY one ofthe members and having cam engagement. with the other of the membersbetween which relative movement is required.

Preferably the cam is so shaped and arranged that the velocity ratio ofthev movement of the operating lever to the relative movement producedthereby increases as the lever moves away from its normal position ofrest.

One of the mem-bers between which relative movement is required may befixed and the operating lever either may be pivoted about a fixed axisand have cam engagement with the movable member.

A modification of the invention includes the provision` of meanscomprising a valve for establishing communication between the chamberand a fluid supply, characterized by means operatively connecting thevalve and the movable member such that the valve is opened only when themovable member reaches or approximates its normal position of rest.

In order that the invention maybe more readily understood, a speciicexample thereof will now be described with reference to the accompanyingdrawing, in which- Figure 1 is an elevation, from what` willbe describedas the frontend, of an apparatus for producing pressure for operatingbrakes, and

Figure 2 is a section on the line 2-2 of Figure 1. A

Like reference numerals indicate like parts in both figures.

The apparatus comprises a cylinder 10 fixed by means of a saddle 11 to`a. member 12= ofthe frame of the machine, or in the case of an aeroplaneto arudder-bar, and having within it a movable piston 13. The skirt ofthe piston is of considerable length and projecting transversely throughit is a Egudgeon pin 14 near the rearward end of it. ach end of the pinprojects througha slot extending parallel to the axis of the cylinderthrough the wallthereof.:

The piston is operated by means of a. pair of L-shaped levers 15 one oneach side of the cylinder, each of which is pivoted at the end of onearm about a fixedV axis 16. Each lot' these levers has a cam slot 17inthe nei hbourhood of its bend to enga-ge one en of the gudgeon pin 14.The other arms off the levers come together and are provided with apedal 18. The piston is normally urged rearwardly by means oftensionsprings 19. The cam engagement between the pin and the le.- vers is suchas to be operative in both directions of movement of the lever. Thus, ifpre# ferred, the retraction of the piston could be eected by a springacting on the operating levers instead of on the piston. I

The iront of the piston is provided with a screwed cap 20 which servesto hold in position a washer 21 forming a fluid-tight joint with thewalls of the cylinder. The opposing face of the cylinder has in it arecess communicating with connector tubes 30, 31 to communicaterespectively with a Huid supply and with the brakes to be operated. Thecommunication with the pipe 30 and fluid supply is, however, normallyclosed b means of a conical valve 22 which is urged'mto a seating 23 bymeans of a spring 24. The valve ls provided .with a stem 25 'extendingthrough an 9 aperture in the cap20 of the piston, and hav- 5 ing at' itsopposite end a head 26. A screwed sleeve 27 fits in this aperture andhas in it a central bore through which the stem 25 but not the head 26can pass. Thus when the pis- 10D ton is in its rearmost position thesleeve 27 will engage the head. of the rod 25 and lift the valve 22 oftits seating. At all other posltions of the piston the valve is closedand communlcation with thefluid supply is cut olf: The aperture in thepiston cap is sealed against escape of pressure fluid by a hollowclosedprojection- 28 formed on the back of the piston cap and affordinga cavity to accommodate. the valve stem.

The cam slots in the operating levers are so arranged that the leverageof the lever on the piston increases as the piston is moved forwardly inthe cylinder, so that for any movement of the lever through a givenangle p the movement of the piston decreases as the piston movesforwardly in the cylinder.

With means according to this invention a comparatively high Huidpressure can be obtained in a liquid system with comparatively smallmovement ofthe lever land without excessive pressure being applied tothe pedal. This is particularly due to the fact that the leverage of thelever in relation to the movement of the piston increases as the pistonmoves forwardly in the cylinder (i. e. to the left in Figure 2).Further, the size of the cylinder and accompaniments can becomparatively small and thus render the means particularly suitable forsuch uses as operating brakes on air-craft wheels.

1.` Pressure-a plying apparatus for iuid` operated wheelrakes comprisingin combinationa cylinder to contain the fluid, a piston slidable withinsaid cylinder, a gudgeon pin projecting transversely through the pistonandextending through longitudinal slots in the cylinder wall, and apair. of L-shaped operating levers one on each side of the cylinfor.establishing communication between the chamber and a fluid supply, saidmeans comprising a valve of conical form, a stem on said valve slidablelengthwise in the aperture 1n the piston in the direction of movement ofthe latter, and a head or enlargement on said stem to be engaged by thepiston just before the latter reaches its normal position of rest -inorder to raise the valve off its seating.

4. Pressure-applying apparatus for fluid- 75 operated wheel-brakescomprising in combination a cylinder to contain the fluid, a piston pslidable within said cylinder and having an aperture therein, anoperating lever for producing-kmovement of the piston and means forestablishing communication between the chamber and a Huid supply, saidmeans comprising a valve of conical form, a stem on said valve slidablelengthwise in the aper-V` der eachpivoted at one end about a xed axisand having a cam slot in the neighborhood .of the bend to engage thegudgeon pin and h aving their other ends joined together forslmultaneous operation.

2. Pressure-applying apparatus for Huidoperated wheel-brakes comprisingin combination a cylinder to contain fluid, a piston slidable withinsaid cylinder and having an aperture therein, an operating lever forproduclng movement ofthe piston and means for establishing communicationbetween the chamber and a fluid supply, said means compr1s1ng a valve, astem on said valve slidable lengthwise in the aperture in the piston inthe direction of movement of the latter and a head or enlargement onsaid stem tovbe engaged by the piston just before the latter reaches itsnormal position of rest in order to open the valve.

3. Pressure-applying apparatus for Huidoperated wheel-brakes comprisingin combination a cylinder to contain fluid, a piston slidable withinsaid cylinder and having an aperture therein, an operating lever forproducing movement of the piston and means vSi)

